1. Field of the Invention
This invention pertains to reinforced structural wood members, such as beams, columns and trusses. More particularly, the present invention pertains to the use of reinforcement panels having a cellulose surface material for improved adhesion to structural wood members.
2. Description of the Related Art
To remain competitive, wood product engineers have had to adopt innovative designs in combination with alternative materials to enhance the structural limits and cost effectiveness of engineered wood products. Examples of engineered wood products include glued laminated wood beams, laminated wood columns, wood I-beams, and wood trusses. The prior art is replete with examples of these engineered wood products.
The preferred method for fabrication of engineered wood products is to connect wood boards with a resorcinol-formaldehyde resin. Resorcinol-formaldehyde is the preferred adhesive because it is low cost, workable, and has a lower toxicity, particularly as compared to epoxy resins.
To improve the effectiveness of engineered wood products, recent studies have looked at using high strength fiber panels as reinforcement. At a 1988 International Conference on Timber Engineering a paper was presented entitled "Reinforced Glued-Laminated Wood Beams" by Mr. Dan A. Tingley (hereinafter "Tingley Paper") that disclosed the use of reinforced plastics (RP) in glued laminated wood beams (glulams). The Tingley paper disclosed test results of glulams using aramid fibers sold under the trademark KEVLAR for reinforced plastic panel(s) located at high stress areas. The results indicated a 19% improvement in ultimate load-to-failure of beams with KEVLAR reinforcement as opposed to nonreinforced beams. However, the Tingley paper does not disclose a method for using resorcinol-formaldehyde resin ("resorcinol") as an adhesive for the RP to wood laminae connection. On the contrary, the Tingley paper teaches away from using resorcinol adhesives by teaching the use of epoxies to adhere the RP to the surrounding wood laminae even though the less expensive commercial adhesive, resorcinol, was used between the other layers of wood laminae.
One method for the attachment of an RP to engineered wood products using resorcinol was disclosed in a parent to the present application, which disclosed the use of fiber-based panels wherein some of the fibers have ends along the length of the panel that protrude from a resin encasement to provide a surface to which resorcinol can bond. Generally, such a panel is created by abrading its surface to create protruding fibers which can then be adhesively adhered to a wood structure. However, many materials are not suitably abradable to create the fiber-protruding surface. Most notable are reinforcement panels constructed using carbon or glass fibers.
What is desired therefore, is a reinforcement panel that can be adhesively adhered to the wood structure, preferably in the same manner as the wood laminae themselves are adhered together, without the need for abrading its surface. Further, such a panel should be resistant to moisture degradation and have dimensional stability. Moisture degradation generally refers to the ability of a material to maintain its integrity when subjected to moisture. Dimensional stability generally refers to the ability of a material to resist shrinking or expanding when subjected to stresses.
Another area of related art is the fabrication process of pultrusion. Pultrusion, shown in FIG. 7, is defined as a continuous manufacturing process for producing lengths of fiber reinforced plastic parts. Pultrusion entails pulling flexible reinforcing fibers through a liquid resin bath and then through a heated die where the plastic part is shaped and the resin is cured. Pultrusion is known for its ability to fabricate a continuous length of reinforced plastics and to accommodate custom placement and orientation of fibers, which allows for the mechanical properties of the pultruded part to be designed for a specific application.